1. Field of the Invention
The present invention relates to a semiconductor device using an adhesive sheet.
2. Background Art
Recently, in accordance with shrinking of a semiconductor device, contamination of a semiconductor device due to a minute amount of metal impurities is becoming a problem. In addition, as a semiconductor chip is rendered three-dimensional and a semiconductor device is highly integrated, reduction in film thickness of the semiconductor chip and adoption of a multilayer structure in the semiconductor chip are realized, whereby there have been increased requirements to more tightly control contamination in the production of the semiconductor device. Therefore, although a process for removing metal impurities is required to be provided, the provision of the process leads to reduction in productivity.
Some of the metal impurities, especially, metal ions such as Cu, Fe, Au, and Na that are movable ions with a high rate of diffusion in a wafer cause a problem. Those metal ions cause crystal defects in a semiconductor device region formed on the wafer, leading to deterioration of characteristics of a semiconductor device or an insulator film.
Thus, methods for removing those metal impurities from wafers have been proposed.
As one of the methods, there is a well-known method for cleaning a wafer with a mixed chemical solution of HCl (hydrochloric acid)-H2O2(hydrogen peroxide)-H2O (purified water) (the mixed chemical solution is referred to as Hydrochloric acid-Hydrogen Peroxide mixture (HPM) cleaning solution).
In the method for wet cleaning a wafer, metal impurities existing on a surface of the wafer can be removed. However, it is difficult to remove metal impurities existing inside the wafer by the method. In addition, naturally, this wet cleaning method requires many processes, facilities, and tightly contamination control. Namely, the wet cleaning method has a big problem in that enormous manufacturing cost is required.
Thus, as a method for removing metal impurities existing inside the wafer, a method referred to as a gettering method has been proposed. In this method, a region (referred to as a gettering site) in which metal impurities are trapped is formed on a wafer, and metal impurities are trapped in the region thereby prevent diffusion of the metal impurities in a semiconductor device region and so on, and a semiconductor device is prevented from being adversely affected by the metal impurities. More specifically, the gettering site is constituted of a set of a plurality of dangling-bonds. The dangling-bonds trap metal impurities. Thus, the gettering site is formed, for example, on the back surface region of a wafer or in the STI (Shallow Trench Isolation) region on the wafer those are regions distant from a semiconductor device region (a semiconductor active region) on a wafer so that even when dangling-bonds trap metal impurities, a semiconductor device and so on are not influenced.
The gettering method includes two main methods: an Extrinsic Gettering (EG) method and an Intrinsic Gettering (IG) method.
In the Extrinsic Gettering (EG) method, a plurality of dangling-bonds is formed on the back surface of a wafer to provide a gettering site. More specifically, the EG method is classified as follows by a method for forming a gettering site.
As a method for forming a generally used gettering site on the back surface of a wafer, there is a Back Side Damage (BSD) method. In this method, the back surface of a wafer is roughen thereby form a plurality of dangling-bonds on the back surface of the wafer, and, thus, to provide a gettering site (this method is disclosed by Japanese Patent Laid-Open No. 1993-29323, for example).
As another method, there is a Polysilicon Back Seal (PBS) method. In this method, a polysilicon film is laminated on the back surface of a wafer to thereby cause a distortion stress on the wafer, whereby a plurality of dangling-bonds are formed on the back surface of the wafer to provide a gettering site (this method is disclosed by Japanese Patent Laid-Open No. 2004-200710, for example).
As still another method, there is a phosphorus gettering method. Highly-concentrated phosphorus is injected into the back surface of a wafer to thereby form a plurality of dangling-bonds. According to this constitution, a gettering site is provided on the back surface of the wafer.
Meanwhile, in the Intrinsic Gettering method, a plurality of dangling-bonds are formed in a predetermined region in a wafer, for example, a STI (Shallow Trench Isolation) region on the wafer and a gettering site is provided. More specifically, in the Intrinsic Gettering method, the gettering site is formed as follows.
A minute amount of oxygen existing in a wafer is, for example, heated to be precipitated as oxide silicon (SiOx) in a predetermined region in the wafer. By virtue of the precipitation of oxide silicon, a plurality of dangling-bonds is formed in a predetermined region in the wafer to provide a gettering site (this constitution is disclosed by Japanese Patent Laid-Open No. 1993-82525, for example).